In recent years, a liquid crystal display incorporates various circuits constituted by a thin film transistor (hereinafter, referred to as “TFT”) in order to improve display performance and reduce power consumption. An existing complementary metal-oxide-semiconductor (CMOS) circuit is used to easily configure various circuits, but a manufacturing process is complicated, such that manufacturing cost increases.
Therefore, a technology in which a circuit such as a scan driver is constituted by only one of N-type and P-type TFTs has been primarily reported. However, the circuit which can be constituted by only the N-type or P-type TFT has been very limited up to now. In particular, a method for effectively configuring the inverter, the NAND gate, and the NOR gate which are basic components constituting a digital circuit has not ever been reported.
FIG. 1 shows an existing inverter circuit constituted by only the N-type TFT.
Referring to FIG. 1, since a pull-up transistor M2 is turned on regardless of an input signal at all times, an output voltage cannot decrease to 0 V and when a pull-down transistor M1 is turned on, current flows between a power voltage VDD and a ground voltage GND, such that power consumption is very high.